Nepal floods: Avalanche raced down Himalayas at 167 kmph, triggering deadly deluge

An ice-rock avalanche in the high Himalayas raced down at speeds of up to 167 kmph, triggering a deadly flood on August 26 in Nepal. A preliminary study by Nepalese scientists revealed that the mass of ice, rock and debris traveled 22 kilometers to Rasuwagadhi in just over seven minutes. The avalanche started from an altitude of about 5,200 meters in the Langtang–Lirung area of Rasuwa, descending steep terrain before reaching the Lhende River at around 2,930 meters.

It then surged downstream through the Bhotekoshi and Trishuli river systems, causing widespread destruction. Satellite imagery showed major geographical changes across 10 square kilometers, with a section of glacier approximately 0.56 square kilometers breaking away. The study ruled out the initial assumption of a glacial lake outburst flood (GLOF), finding no evidence of such an event.

Water levels and river flow in affected areas fell several hours before the destructive surge arrived, challenging the theory that heavy rainfall alone caused the floods. The avalanche resulted in extensive damage to Nepal's hydropower infrastructure, with 13 hydropower projects and one solar project affected, taking around 431 MW of generation capacity out of the system.

At least 900 people were killed, with thousands still missing as rescue teams continued to search for workers trapped inside hydropower tunnels in the worst-hit districts of Rasuwa and Nuwakot. Concerns have been raised about further landslides, unstable glaciers, and potentially dangerous lakes, indicating that the Himalayan region could face additional flooding even after the initial torrent has passed.